Effect of Environment on Nutrient Requirements of Domestic Animals (1981) / Chapter Skim
Currently Skimming:
DAIRY CATTLE
DAIRY CATTLE
Pages 75-84
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 75... ...
The major reasons are that dairy cattle are not usually fed for maximum growth rate or full genetic potential for milk production, and the management systems create either micro- or macroenvironments that affect maintenance needs of the animals. Dairy animals are generally kept: (1)
|
From page 76... ...
The nutritive requirements are also confounded by stage of lactation effects on milk yield. THERMAL ZONES FOR DAIRY CATTLE Except for the neonatal calf, the estimated range of temperature for highest efficiency of energy utilization is about 13-18°C; however, significant changes in feed intake or in numerous physiological processes will not usually occur within the range of 5-25°C (McDowell, 1972~.
|
From page 77... ...
It appears, therefore, that level of feeding and care to ensure thriftiness in female dairy calves is more important than maximizing rate of growth. When male calves of dairy breeds are fed to maximize growth rate, the guidelines on requirements for various environments described for beef cattle appear appropriate.
|
From page 78... ...
z LU 125 A: ° 3= uJ ~ ~ 3, UJ 100 zo adz c ~ in ~ E Z ~ - o FIGURE 17. Estimated maintenance requirements for a 600-kg cow over a temperature range of-15 to + 40°C; percentage changes intake of dry matter under low and high temperatures expressed as percentage of level at 1 8-20°C for cows consuming ration of 60 percent roughage and 40 percent concentrates (60 R)
|
From page 79... ...
, coupled with usually lowered palatability of such feeds as frozen silage at-IS to - 20°C, the expected dry matter intake will increase to only 20.4 kg per day. With rising TABLE 21 Relative Changes in Maintenance Requirements and Dry Matter for 600-kg Cows Producing 27-kg 3.7 Percent Fat Milk at Various Ambient Temperatures Along with Estimates of Actual Intakes of DM and Water Requirement for 27-kg Production Expectedc Temperature Maintenance DMb DM Intake Milk Water Intake (oc)
|
From page 80... ...
Shifting of the concentrate ratio will enable cows to maintain ME intake nearer the level required to maintain 600-kg body weight and 27-kg milk yield per day over a wider temperature range than on diets higher in roughage content (Figure 17, 20 R)
|
From page 81... ...
Further evaluations of seasonal effects on the nutritive requirements for heifers is desirable. Lactating Cows According to the values in Figure 17 and Table 21, maintenance requirements for a 600-kg Holstein will rise markedly when exposed for 6 h or more per day to temperatures above 30°C, a relative humidity of 70 percent or higher, and solar radiation exceeding 700 langleys per day.
|
From page 82... ...
Although the Phoenix area cows were exposed to the highest temperatures, the low humidity and rapid cooling of the environment after sunset permitted restoration of heat balance and higher feed intake. The New York cows were exposed to the fewest hours above 27°C, but feed intake was markedly affected by high humidity and poor acclimatization to the heat stress due to only short periods of high temperatures.
|
From page 83... ...
SUMMARY The feasibility both from the standpoint of economics and biological efficiency for supplying additional feed for higher maintenance needs of calves and heifers of dairy breeds under hot or cold conditions is not clear at this time. It seems that except under extreme circumstances for calves or heifers in later stages of pregnancy, added feed is not practical as compensatory gains in other periods will occur.
|
From page 84... ...
Use of breeds smaller than Holstein or cross-brads may give the appearance of improved efficiency under extreme thermal conditions; but when considered on the input-output ratio per unit of metabolic size, the validity of changing breeds to increase gross efficiency becomes less convincing. The general conclusion is that improved information is needed to provide more accurate guidelines on feeding dairy cattle in various environments, particularly under field situations.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.